1. Field of the Invention
The invention relates to fiber optics. More particularly, the invention relates to an optical subassembly and related methods for aligning an optical fiber with a light emitting device.
2. Brief Description of the Prior Art
One of the most critical components in any fiber optic system is the interface between electrical and optical components. In high bandwidth telecommunications applications, for example, it is critical that an accurate transition be made between the optical and electrical components. One of the single most important development in bringing fiber optic telecommunications to the home and office is the emergence of a new generation of small form factor fiber connectors.
When fiber was first being laid in long distance networks, fibers had to be spliced together using special splicing kits applied by skilled personnel. The advent of standardized ST and SC fiber connectors reduced the cost of fiberization, encouraging the use of fiber. But it was not enough to make fiber-to-home and fiber-to-desk schemes cost effective except in the few cases where fiber rather than copper was effectively mandated by exceptionally high bandwidth, security, or interference requirements.
The new breed of small form factor (SFF) connectors are about the same size as the RJ45 connectors used for twisted pair telephone systems and LANs. This compares with a more traditional fiber optic connector, which is about twice the size of an RJ45. SFF connectors have a lower unit cost than traditional connectors and they are built for easy, xe2x80x9csnap-inxe2x80x9d installation. SFF connectors therefore reduce the cost of fiber-to-the-x, both directly and through reducing the cost of installation.
Since the introduction of fiber optic connectors in the 1970s, there have been many different methods of retaining the fiber in the precise alignment necessary to insure minimum light loss and to minimize reflections between joined sections of cable. One prior art method utilizes lenses and another utilizes a ceramic sleeve to align with a ferrule carrying a fiber polished on both ends. Both of these methods have drawbacks. The lensing system required extremely precise alignment to achieve sufficient transmission accuracy. The ceramic sleeve approach provides much higher accuracy but is much more expensive to produce.
It is therefore an object of the invention to provide an optical subassembly and related methods for aligning an optical fiber with a light emitting device.
It is also an object of the invention to provide an optical subassembly and related methods for aligning an optical fiber with a light emitting device which can be fabricated utilizing an automated assembly process.
It is another object of the invention to provide an optical subassembly and related methods for aligning an optical fiber with a light emitting device which can be built with standard laser welding machines.
It is still another object of the invention to provide an optical subassembly and related methods for aligning an optical fiber with a light emitting device which inexpensive to manufacture.
In accord with these objects which will be discussed in detail hereinafter, one embodiment of the invention contemplates apparatus for coupling a light emitting device to the mating fiber of a connector comprising a ferrule; and a fiber stub mounted in the ferrule. The fiber stub, according to the invention, has a fixed end substantially flush with the surface of the ferrule and a loose end extending beyond the surface of the ferrule.
According to another embodiment of the invention, a ferrule and fiber stub mounted in the ferrule (again, the fiber stub having a fixed end substantially flush with the surface of the ferrule and a loose end extending beyond the surface of the ferrule), are combined with a light emitting device (held by first mounting means for holding the light emitting device), using a second mounting means (for holding the ferrule with the fiber stub mounted therein) adapted to be welded to the first mounting means.
A further aspect of the invention is directed to an optical subassembly for aligning an optical fiber with a light emitting device of including a fiber optic stub mounted in a ferrule used with a v-groove device. The v-groove device receives a loose end of the fiber optic stub, for alignment of the loose end with a mating fiber of a connector also placed in the v-groove device. The other end of the fiber optic stub is polished.
According to a this embodiment of the invention, the ferrule is mounted in a ring which is welded to a light emitting subassembly. The invention contemplates self aligning the unpolished loose end of the fiber optic stub with the mating fiber in the v-groove device.
According to the presently preferred embodiment, the v-groove device is provided with one or more s-bends which aid in self-alignment between the loose fibers.
Still further, the invention contemplates a method for coupling a light emitting device to the mating fiber of a connector, comprising the steps of (a) mounting a fiber stub in a ferrule such that a first end of the fiber stub is mounted substantially flush with a first surface of the ferrule and a second end of the fiber stub extends beyond a second surface of the ferrule; (b) utilizing a mounting ring to hold the ferrule and fiber stub mounted therein; and (c) aligning the mounting ring containing the ferrule and the fiber stub with a light beam emitted from a light emitting device so that the first end of the fiber stub and the light beam are brought into substantial alignment.
According to a presently preferred embodiment of the invention, the aforestated method further comprises the step of polishing the first end of the fiber stub.
Further methods contemplated by the invention include fixing the position of the mounting ring containing the ferrule and the fiber stub, relative to the light beam emitted from the light emitting device once the first end of the fiber stub and the light beam are brought into substantial alignment; and self aligning the second end of the fiber stub extending beyond the second surface of the ferrule, with the mating fiber of a connector utilizing a v-groove device.
According to a presently preferred embodiment of the invention, the aforestated methods further comprise the steps of welding the mounting ring to means for holding the light emitting device; utilizing a v-groove containing at least one s-bend; and performing the assembly process contemplated by the invention automatically.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.